Optical element having antireflection film, and exposure apparatus

Abstract

An optical element includes a substrate that transmits a light having a central wavelength in a wave range between 150 nm and 250 nm, and an n-layer antireflection film that is formed on the substrate, and includes, from the substrate, an n−2-th layer made of a high refractive index material, an n−1-th layer made of an amorphous material containing AlF 3 , and an n-th layer made of a low refractive index material, each of the high and low refractive index materials containing a crystalline material.

1. An optical element comprising:
 a substrate that transmits a light having a central wavelength in a wave range between 150 nm and 250 nm; and 
 an n-layer antireflection film that is formed on the substrate, and includes, from said substrate, an n−2-th layer made of a high refractive index material, an n−1-th layer made of an amorphous material containing AlF 3 , and an n-th layer made of a low refractive index material, each of the high and low refractive index materials containing a crystalline material, wherein n is an integer greater than or equal to 4. 
 
   
   
     2. An optical element according to  claim 1 , wherein said n-layer antireflection film further includes, from said substrate, an n−3-th layer made of an amorphous material containing AlF 3 . 
   
   
     3. An optical element according to  claim 1 , wherein the low refractive index material is selected from CaF 2 , MgF 2 , BaF 2 , AlF 3 , NaF, LiF, SrF 2 , Na 3 AlF 6 , Na 5 Al 3 F 14 , and a composite material of two or more of CaF 2 , MgF 2 , BaF 2 , AlF 3 , NaF, LiF, SrF 2 , and Na 3 AlF 6 , Na 5 Al 3 F 14 , and the high refractive index material is selected from NdF 3 , LaF 3 , YF 3 , GdF 3 , DyF 3 , PbF 2 , and a composite material of two or more of NdF 3 , LaF 3 , YF 3 , GdF 3 , DyF 3 , and PbF 2 . 
   
   
     4. An exposure apparatus comprising an optical element according to  claim 1 , and using the optical element to expose a plate. 
   
   
     5. A device manufacturing method comprising:
 exposing a plate using an exposure apparatus that includes an optical element according to  claim 1 ; 
 developing the plate that has been exposed. 
 
   
   
     6. An optical element comprising:
 a substrate that transmits a light having a central wavelength in a wave range between 150 nm and 250 nm; and 
 an n-layer antireflection film that is formed on the substrate, and includes, from said substrate, an n−1-th layer made of a high refractive index material, an n-th layer made of a low refractive index material and an amorphous material containing AlF 3 , each of the high and low refractive index materials containing a crystalline material, wherein n is an integer greater than or equal to 2. 
 
   
   
     7. An exposure apparatus comprising an optical element according to  claim 6 , and using the optical element to expose a plate. 
   
   
     8. A device manufacturing method comprising:
 exposing a plate using an exposure apparatus that includes an optical element according to  claim 6 ; 
 developing the plate that has been exposed.